The Physiology Core is a new component of the DRTC that consolidates the expertise and experience related to in vivo measures of parameters of glucose tolerance and physiological regulation of carbohydrate metabolism accumulated over more than 15 years by DRTC investigators. This Core will assist in a wide array of in vivo procedures for assessing insulin secretion, insulin sensitivity, and factors regulating glucose tolerance. It will provide consultative, technical, analytical and interpretative support. Since recent work by DRTC investigators has shown that sleep loss may be a risk factor for the metabolic syndrome and epidemiology studies indicate that up to 40% of diabetic patients have sleep-disordered breathing, the Physiology Core of the University of Chicago DRTC will also include the unique feature of offering services related to sleep assessment. The Core will maintain three IRB-approved master protocols for human studies (General Clinical Research Center studies of glucose regulation; Ambulatory evaluation of glucose regulation; Assessment of sleep-wake regulation and sleep-disordered breathing) and one ACUC-approved protocol for studies of parameters of glucose tolerance in mice (mostly genetically manipulated animals). This new Core was instituted to ensure that all independently funded investigators involved in diabetes research at the University of Chicago have access to a wide range of well-validated, standardized methods for in vivo evaluation of parameters of glucose tolerance. The services offered by the Core will facilitate the phenotyping of parameters of glucose tolerance in both humans and mice while avoiding the proliferation of multiple independent protocols involving variable testing procedures. It is also expected that the Core will greatly improve quality control and cost effectiveness, promote communication and exchanges among investigators and represent an outstanding training opportunity for junior investigators. Eve Van Cauter, Ph.D., a clinical investigator who has experience in leading multidisciplinary teams, will serve as Director and Robert L. Rosenfield, M.D., Associate Program Director of the General Clinical Research Center, will serve as Co-Director.